1. Technical Field
This invention relates generally to second stage tire building machines and, more particularly, to a bladderless second stage tire building machine. Specifically, the present invention relates to a former sleeve for a bladderless second stage tire building machine that is held in position by the existing clamps and substantially encloses the expandable bead lock shoes such that the sleeve is clamped between the shoes and a tire carcass to form a strong and reliable seal.
2. Background Information
In a two-stage tire building operation, a substantially cylindrical tire carcass is first built by a carcass former. Thereafter, the carcass is dismounted from the carcass former and transferred and mounted on a second stage tire building machine. The second stage tire building machine expands the tire carcass into a rough tire shape such that it may be mated with a tread package.
The tire carcass is expanded by sealing its outer edges and filling its interior with pressurized air. The pressurized air causes the body of the tire carcass to expand outwardly while the second stage tire building machine pushes the edges of the tire carcass inwardly so that a rough tire shape is formed. The tread package is mated with the outer surface of the tire carcass while the pressurized air holds the shape of the carcass. The carcass and tread package may then be rotated to allow for bonding and stitching of the different layers.
One type of second stage tire building machine known in the art utilizes a bladder disposed between two bead lock assemblies to provide the required expansive force. An example of this type of machine is depicted in FIGS. 1 and 2. Although functional, the second stage tire building machine utilizing the air bladder has certain disadvantages given the expense of providing the bladder which must be replaced as it is repeatedly used. Such disadvantages led the industry to develop a bladderless second stage tire building machine.
One embodiment of a bladderless second stage tire building machine known in the prior art is schematically depicted in FIGS. 3 and 4 of the present specification. The bladderless machine includes a pair of bead lock assemblies movably carried on a main shaft. As can be seen in FIGS. 3 and 4, the bladder of FIGS. 1 and 2 is absent. Instead, the seal is created by a pair of flexible, annular seals that are held at one end by the existing clamp and at the other end by a clamping groove formed in each of the bead lock shoes of the bead lock assemblies. The clamping arrangement may be seen in FIGS. 5 and 6 of the present specification. This arrangement is functional although the seal is relatively thin between the area of high pressure inside the tire carcass and the external atmosphere. Furthermore, the cost of retrofitting a machine using a bladder with the bladderless bead lock shoes is undesirably high.
In view of the foregoing, it is clear that there is a need in the art to provide a bladderless former sleeve for a second stage tire building machine that creates a strong and reliable seal during tire carcass expansion while providing a configuration that allows for relatively easy and inexpensive retrofitting. It is further desirable that the bladderless former sleeve is able to be installed on a second stage tire building machine without requiring the machine to be modified structurally.